The present invention is particularly intended for use on commercial vehicles, although it may be used with any internal combustion engine connected to a fuel tank having a draw and return tube assembly. In particular, diesel engines typically operate by drawing fuel from a fuel tank, combusting a portion of the fuel and then returning the unused, or uncombusted, fuel to the fuel tank. The volume of fuel returned to the fuel tank is dependent on engine power output, and generally is quite substantial. Accordingly, such draw and return tube assemblies play a vital role in the operation of diesel engines.
Heavy commercial vehicles frequently employ dual fuel tanks, also called saddle tanks, wherein fuel is drawn simultaneously from both tanks for combustion within the engine. To prevent uneven draw and return of the fuel, which may lead to air being drawn into the engine, fuel flow regulators, such as draw and return tube assemblies, typically are installed in each of the dual fuel tanks.
One prior art draw and return tube assembly comprises draw and return tubes connected to a flange at one end of the tubes. The flange typically is mounted at an aperture sized to receive the flange on an outside surface of the fuel tank such that the opposite end of each of the draw and return tubes extends downwardly into fuel held within the lower portion of the tank. Draw and return lines from the engine are connected to the draw and return tubes at the flange, outside the tank.
The tube end openings inside the tank and opposite the flange typically extend away from one another and are each positioned an equal distance from the flange so that the draw and return tube fuel openings are also each positioned an equal distance below the top surface of fuel held within the tank. In this arrangement, when the two saddle tanks and the corresponding draw and return tube assemblies are each positioned on the commercial vehicle, the pressure head of fuel positioned above the draw and return tube openings of each assembly will result in equal amounts of fuel being withdraw from each of the tanks and equal amounts of fuel being returned to each of the tanks. In addition, swedging or crimping of the end of the return tube opening opposite the flange will facilitate filling the return fuel line. This filling of the return fuel line enables a siphon effect between the left and right hand fuel tanks. Accordingly, the draw and return tube assemblies of the prior art act as passive flow regulators for ensuring equal levels of fuel drawn and returned to each of the two saddle fuel tanks.
Conventional draw and return tubes may be extruded and then machined to enlarge their size or change their shape, whereafter the machined tubes are welded directly to the flange. The weld site at the flange may experience stress and related damage during bumpy movements of the truck along a road due to the large mass of material located remote from the flange, i.e., due to the long fuel tubes extending from the flange. A fuel tube having a relatively large thickness may be required in such prior art designs so as to withstand stress during welding to the flange and so as to withstand stress at the flange/tube connection during bumpy movement of the truck along a road. The large mass of material used to manufacture the thick draw and return tubes may contribute to high manufacturing costs of prior art assemblies.
Accordingly, there is a need for a draw and return tube assembly that may reduce stress on the flange and may be manufactured at a less expensive cost.